Manufacture of artificial filamentary materials



Nov. 27, 1962 R. J. BROWN ETAL 0 MANUFACTURE OF ARTIFICIAL FILAMENTARY MATERIALS Filed June 25, 1956 United States Patent Otltice 3,066,007 Patented Nov. 27, 1962 3,066,007 MANUFAQTURE F ARTIFICIAL FILAMENTARY MATERIALS Russell Jacques Brown and John Downing, Spondon, near Derby, England, assignors to British Celanese Limited, a company of Great Britain Filed Ziuue 25, 19:50, Ser. No. 593,392 Claims priority, application Great Britain July 11, 1955 13 Claims. (Cl. 1854) This invention relates to the manufacture of artificial filamentary materials by wet spining processes, and especially to the manufacture of materials of highdenier, which may for example be used as tow for conversion into staple fibre.

In one method of making a wet spun tow of artificial filamentary material, untwisted filament bundles from several spinning positions are combined, preferably after they have left the coagulant and before they are freed from coagulant. In such a process it is desirable after bringing the several bundles together to draw the tow so formed over a friction device adapted to wipe off part of the coagulant which still adheres to the filaments, and then to pass the tow to a Washing device in which the coagulant is substantially completely removed.

We have found that when working in this way there is often a considerable tendency for the several bundles to separate somewhat after leaving the friction device, and also for the individual filaments in each bundle to cohere so that the tow when it leaves the friction device on its way to the washing device is undesirably still.

The present invention provides a method of overcoming or mitigating these two difficulties simultaneously.

According to the invention, in a process in which filamentary material is made by a wet spinning method, and after leaving the coagulant passes over a stationary friction device adapted to remove adherent liquid from it on its way to a washing device, there is applied to the material shortly or immediately before or as it leaves the friction device a liquid which is freely miscible with the coagulant and also with the liquid to be used for washing the material and which is substantially without solvent or swelling action on the substance of which the filaments are made. Advantageously used washing liquid is applied to the material. Such used washing liquid naturally contains coagulant and when the coagulant comprises a solvent or swelling agent for the filamentary material, e.g. in aqueous solution, the used washing liquid applied to the material may with advantage contain about l2% by weight of such solvent or swelling agent.

While the main advantage of the invention results from its use in a process in which filament bundles from a number of spinning positions are brought together in advance of the washing device to form a tow, especially a tow of denier about 10,000 or higher, it is also applicable to wet spinning processes for making material of sub stantially lower denier, whether they make use of a number of spinning positions or only one position in the pro 'duction of each end of material. 7

The invention is of particular value in the production of cellulose acetate tows by wet spinning an acetone solution of the cellulose acetate using as the coagulant an aqueous solution of a swelling agent or solvent for the cellulose acetate which boils at a temperature considerably above 100 C., and thus cannot conveniently b removed from the tow simply by evaporation. A particularly useful example of such a process is the extrusion of an acetone solution of cellulose acetate into an aqueous solution of diethylene glycol diacetate, and it will be convenient in describing the invention in more detail to refer specifically to this process. The invention may however be applied to the manufacture of filamentary materials from other starting materials or using other spinning solvents or coagulants; for example it may be used in making a cellulose triacetate tow by spinning an acetic acid so1ution of cellulose triacetate into aqueous acetic acid, or a solution of cellulose triacetate in a mixture of methylene chloride and methanol or ethanol into methanol or ethanol. (The term cellulose triacetate is used to denote cellulose acetates having an acetyl value, reckoned as acetic acid, above 59% and especially above 60% A form of apparatus embodying the invention is illustrated diagrammatically in the accompanying drawing, in which the FIGURE is a side view, partly in section, of the apparatus.

Referring now to the drawing, the apparatus comprises a number of wet spinning devices 21 each provided with a stripping roller 22. A suitable form of spinning device including a stripping roller is that described and illustrated in US. application Ser. No. 499,166, filed April 4, 1955, now Patent No. 2,895,790, but it will be understood that the invention can also be applied when spinning devices of other forms are used, e.g. devices in which the filaments are extruded horizontally and travel along a trough containing the coagulant. Each spinning device is provided with a godet 1 having an associated skew idler roller 1a, whereby the filaments are drawn from the coagulant. (For the sake of clarity only one spinning device, stripping roller and godet are shown.) Each godet 1 draws a filament bundle 2 from the wet spinning device, and forwards it to a yarn guide 3 by means of which the several bundles are collected to form a single tow 4. The filament bundles 2 may if desired travel directly from the spinning devices 21 to the godets l, or they may first have passed over or through a stripping device other than the stripping roller of U8. application Ser. No. 499,166, W Patent No. 2,895,790, e.g. an inverted funnel as described in US. application Ser. No. 451,190, filed August 20, 1954, and now Patent No. 2,911,674.

A friction device comprising a set of smooth horizontal friction bars 5 is situated beyond the yarn guide 3. These bars are parallel, but have their axes slightly offset, the operative surfaces of alternate bars being in different planes, so that the tow 4 in passing between them follows a slightly zig-zag path, the arrangement being such that the tow passes alternately over and under adjacent bars and always passes over the final bar of the series.

From the friction bars 5 the tow passes to a washing device 6 of the type described in more detail in US. application Ser. No. 510,754, filed May 24, 1955, and now abandoned. This washing device comprises a pair of positively driven thread-storing thread-advancing rollers 7 and 8 arranged vertically one above the other, and carried in adjustable bearings (not shown) in a vertical supporting member 9. (Thread-storing thread-advancing rollers are hereinafter referred to simply as advancing rollers) By means of the adjustable bearings the axes of the rollers 7 and 8 can be set at varying anglesto the horizontal, and in operation they are set skew with respect to each other so that the tow travels along the rollers in the direction away from the supporting member 9. In addition the lower roller 8 is set at an angle of a few degrees to the horizontal, sloping downwards towards the supporting member 9. The diameters of these rollers may increase in a few steps or smoothly near their input ends to prevent sagging of the tow, as described in US. application Ser. No. 510,754, and now abandoned. Above the higher end of the lower roller 8 is a nozzle l0 fed by a pipe 11, by means of which washing liquid can be sprayed onto the upper surface of the roller. Below the roller 8 a trough 12, provided with a constant level run-oil 13, is positioned to receive washing liquid falling from the roller. A line 14 containing a small pump 15 leads from the run-01f 13 to a nozzle 3 16 situated immediately above the tow as it passes over the final bar of the friction device.

A godet 17 of the type described in US. application Ser. No. 429,307, filed May 12, 1954, and now Patent No. 2,889,034, comprising a short cylindrical section 18 from which extend a number of parallel thread-carrying bars 19, serves to draw the wet tow 4 from the washing device and to deposit it in a sliver can 20 which may be rotated in the known manner to facilitate the packing of the tow in the can.

As an example the use of this apparatus, a number of untwisted cellulose acetate filament bundles formed by wet spinning an acetone solution of cellulose acetate into aqueous diethylene glycol diacetate are drawn from their respective spinning devices 21 over the stripping rollers 3 22 by the godets 1, and fed to the yarn guide 3 where they unite to form the tow 4. For example there may be 5 to 12 such bundles, each comprising l,0002,000 filaments or more and having a denier of 2,0006,000 or more. Although on their way to the godets 1 the filament bundles have passed over a stripping roller or other form of stripping device as already described, when they reach the yarn guide 3 they are still contaminated with a considerable proportion of aqueous diethylene glycol diacetate. As the tow passes between the friction bars 5, part of this residual aqueous diethylene glycol diacetate is wiped off, and as it passes over the final bar it is sprayed with used washing liquid, which may be either a more dilute aqueous diethylene glycol diacetate or a mixture of an alcohol, water and diethylene glycol diace- 3 tate, according to the washing agent used.

The tow then makes a large number of turns round the rollers 7 and 8 of the washing device 6 while the washing liquid, which may be either water or a fairly concentrated or substantially anhydrous lower alkyl alcohol (i.e. an alcohol of formula C H OH where n is 1, 2 or 3), especially ethyl alcohol, is applied by the nozzle 10 to the higher end of the lower roller 8. The washing liquid flows down the surface of the roller 8, and thus washes the tow in counter-current fashion as it travels along the rollers. At the lower end of the roller 8 the Washing liquid falls off into the trough 12, which also serves to collect liquid falling from the roller before it reaches the lower end thereof. The bulk of the liquid so collected, which may contain about 811% of diethylene glycol diacetate, is passed to a solvent recovery plant through the run-off 13, but a small proportion is drawn by means of the pump through the line 14 and applied by means of the nozzle 16 to the tow passing over the final friction bar 5 as already described.

The number of turns made by the tow round the rollers 7 and 8 and the other washing conditions are preferably so chosen that on leaving the washing section the tow carries with it less than 1% of its weight of diethylene glycol diacetate together with of course a much greater proportion of the washing liquid. The wet tow is now deposited by means of the godet 17 in the sliver can 20. If desired it may be further treated in this can; for example, it may be dried in the can, for instance by passing a current of hot air through it, or it may be saponified by means of sodium hydroxide or another suitable saponifying agent. On the other hand the wet tow may be drawn from the can and either dried or given any other desired treatment after being wound on bobbins or the like or for example while it passes round a pair of advancing rollers or an advancing reel. If a material of high extensibility is required, it is preferred to dry the tow in a sliver can or under other conditions such that it is free to shrink by 75-100% of the amount by which it would shrink in the complete absence of tension; for instance it may be dried in the form of banks, or continuously while passing round suitably tapering advancing rollers. (Drying under such conditions is effective in promoting high extensibility in the wet spinning of acetone solutions of cellulose acetate generally, especially when aqueous diethylene glycol diacetate or aqueous acetone is used as the coagulant.)

The invention is of course not limited to the use of the apparatus described above. For example the filament bundles may travel directly from the spinning devices to the yarn guide 3, being drawn for example by means of a godet situated between the bars 5 and the washing device 6, or by the action of the washing device itself. If the spinning devices are suitably arranged the yarn guide 3 may be dispensed with, the bundles coming together naturally of their own accord on the friction bars 5. Different kinds of washing devices may be used; for example the tow may be caused to pass round several pairs of advancing rollers or over several advancing reels, at least one of each pair of rollers, or each reel, either dipping into a bath of washing liquid or having washing liquid applied to its surface or to the tow passing over it. Again, instead of being deposited in a sliver can the wet tow may be wound up and dried in package form or continuously dried, e.g. on a pair of heated advancing rollers or on an advancing reel, either under tension or while free to shrink.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the manufacture of tows in which a plurality of untwisted bundles of wet spun artificial filaments still carrying coagulating liquid derived from the coagulating bath employed in the spinning operation are united to form a tow which passes over a friction device by means of which part of the adherent coagulating liquid is removed from it, and liquid not so removed by friction is subsequently washed out of the tow, which comprises the improvement of applying to the tow after some adherent liquid has been removed from it by friction but before the tow has left the friction device a liquid which is substantially without swelling action on the material of which the filaments are made and which is miscible both with the coagulating liquid and also with the liquid to be used for washing the tow.

2. Process according to claim 1, wherein a tow of denier at least 10,000 is formed.

3. Process according to claim 1, wherein a small proportion of the used washing liquid is applied to the tow.

4. Process according to claim 3, wherein the coagulating liquid is a mixture of a solvent and a non-solvent for the material of which the filaments are made, and the used washing liquid applied to the tow consists of 5 to 12% by weight to the said solvent and to 88% by weight of non-solvent for the said material.

5. A process for the manufacture of cellulose acetate tows, which comprises forming a plurality of untwisted bundles of cellulose acetate filaments by extruding a solution of a cellulose acetate into a coagulating liquid consisting of a mixture of a non-solvent and a solvent for the cellulose acetate, bringing the said bundles together to form a tow, removing part of the coagulating liquid adhering to the tow by passing the tow over a friction device, subsequently continuously washing the tow until substantially all the solvent for the cellulose acetate not removed by friction has been washed out of the tow, and applying to the tow after some of the adherent coagulating liquid has been removed from it by friction but before it has left the friction device and before it is washed a liquid which is substantially without swelling action on the cellulose acetate and which is miscible with the coagulating liquid and also with the liquid to be used for washing the tow.

6. Process according to claim 5, wherein an acetone solution of cellulose acetate is extruded into a coagulating liquid consisting of an aqueous solution of diethylene glycol diacetate.

7. Process according to claim 5, wherein a small proportion of the used washing liquid is applied to the tow.

8. Process according to claim 6, wherein a small proportion of the used washing liquid is applied to the tow.

9. Process according to claim 8, wherein the liquid applied to the tow contains 5 to 12% by weight of diethylene glycol diacetate.

10. Process according to claim 5, wherein the tow is Washed with at least one liquid of formula C H OH where n is 0-3.

11. Process according to claim 9, wherein the tow is Washed with at least one liquid of formula C H- OH where n is 0-3.

12. Process according to claim 1, wherein the filament bundles travel in a zig-zag path over the friction device and adherent liquid is removed by friction from opposite sides of the bundles.

13. Process according to claim 11, wherein the filament bundles travel in a zig-zag path over the friction device and adherent aqueous diethylene glycol diacetate is removed from opposite sides of the bundles.

References Cited in the file of this patent UNITED STATES PATENTS 

1. PROCESS FOR THE MANUFACTURE OF TOWS IN WHICH A PLURALITY OF UNTWISTED BUNDLES OF WET SPUN ARTIFICAL FILAMENTS STILL CARRYING COAGULATING LIQUID DERIVED FROM THE COAGULATING BATH EMPLOYED IN THE SPINNING OPERATION ARE UNITED TO FORM A TOW WHICH PASSES OVER A FRICTION DEVICE BY MEANS OF WHICH PART OF THE ASHERENT COAGULATING LIQUID IS REMOVED FROM IT, AND LIQUID NOT SO REMOVED BY FRICTION IS SUBSEQUENTLY WASHED OUT OF THE TOW, WHICH COMPRISES THE IMPROVEMENT OF APPLYING TO THE TOW AFTER SOME ADHERENT LIQUID HAS BEEN REMOVED FROM IT BY FRICTION BUT BEFORE THE TOW HAS LEFT THE FRICTION DEVICE A LIQUID WHICH IS SUBSTANTIALLY WITHOUT SWELLING ACTION ON THE MATERIAL OF WHICH THE FILAMENTS ARE MADE AND WHICH IS MISCIBLE BOTH WITH THE COAGULATING LIQUID AND ALSO WITH THE LIQUID TO BE USED FOR WASHING THE TOW. 